Lithium titanate is under development as a material of electricity storage devices, and is used in the electricity storage devices as an electrode active material that is advantageous in terms of safety and life characteristics, and especially in lithium secondary batteries as a negative electrode active material. The lithium secondary batteries are spreading rapidly for use as small batteries such as mobile devices' power sources, and are also being developed into large lithium secondary batteries for power generation industries and automobiles. Long-term reliability and high input/output characteristics are required for electrode active materials for such large lithium secondary batteries, and lithium titanate that is advantageous in terms of safety and life characteristics is a promising material as a negative electrode active material.
As described in, e.g., Japanese Unexamined Patent Application Publication No. H06-275263 (Patent Literature 1), there are some compounds as such lithium titanate. For example, as lithium titanate represented by the general formula “LixTiyO4,” compounds satisfying 0.8≦x≦1.4 and 1.6≦y≦2.2 are described, and LiTi2O4, Li1.33Ti1.66O4, Li0.8Ti2.2O4, etc. are shown as representative examples. Known methods for producing such lithium titanate include a wet method in which a predetermined amount of lithium compound and a predetermined amount of titanium compound are mixed in a solvent and the mixture is dried and then baked (Japanese Unexamined Patent Application Publication No. 2001-213622: Patent Literature 2), a spray drying method in which the drying in the wet method is performed by spray drying (Japanese Unexamined Patent Application Publication No. 2001-192208: Patent Literature 3), a dry method in which a predetermined amount of lithium compound and a predetermined amount of titanium compound are mixed in a dry state and the mixture is baked (Japanese Unexamined Patent Application Publication No. H06-275263: Patent Literature 1, Japanese Unexamined Patent Application Publication No. 2000-302547: Patent Literature 4), etc.